Deep levels in Si- and Be-coimplanted GaAs

Deep levels and electrical properties in Si- and Be-coimplanted semi-insulating GaAs, grown by liquid-encapsulated Czochralski methods, were investigated. The Si implantation with a dose of 8×10¹² ions cm^-2 and energy of 65 keV was performed into GaAs already implanted with a Be dose of 2×10¹² cm^-2 and 90 keV for the purpose of an abrupt implant profile in a deeper region. During the Be coimplantation, an electron deep level at 0.62 eV below the conduction band and a hole deep level at 0.68 eV above the valence band were newly observed. In the Be-implanted region of ion-implanted GaAs, the deep levels E_c - 0.62 eV and E_v + 0.68 eV dominate, but are not found in the bulk. From this work, it is suggested that the E_c - 0.62 eV trap could be the defect due to the implantation damage and that the E_v + 0.68 eV trap could be the Be complex related to a Si dose during the implantation.